nForce4 Ultra Reference Board Examination
NVIDIA's reference boards for nForce have traditionally been fairly oddball. Lots of bare PCB real-estate and off-the-wall component placement is usually the norm. nForce4 bucks that trend though, with a reference board design that's aped pretty closely by the three finished retail boards I've had the pleasure of seeing up-close. So it's worth covering the reference board in a little more detail than I usually would.
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The first thing that's interesting with regards the reference board, before we even cover layout, is that it's an 8-layer PCB. Expensive to manufacture and definitely something that'd be strange to see on shipping retail boards, even those very high-end enthusiast boards from the likes of Gigabyte, it's nevertheless a curiousity to note. Look for retail boards to feature 4 or 6-layer PCB designs.
Layout wise, the first thing we come across when looking at the board and going from top to bottom, left to right, is the CPU power circuitry. Looking to be three-phase in delivery, it feeds the CPU socket adjacent. An AMD-enforced socket area surrounds the socket itself. nForce4 boards require the exact same mounting mechanism for heatsinks as seen on all AMD64 boards since the beginning. Dual 64-bit memory channels to the CPU on the Socket 939 CPUs means a quartet of 184-pin DDR DIMM slots next to the socket area. Alternate slots feed a memory channel, so install memory (at least on the reference board) with DIMM pairs starting closest to the CPU, leaving the two furthest away from the CPU free, then fill those second if needed.
24-pin EPS power is a new feature for AMD mainboards, NVIDIA following Intel's lead in powering PCI Express mainboards by using the, until recently, server-oriented power connector on consumer mainboards. The extra four pins over a normal ATX power connector are for supplying power to the PEG16X slot your graphics card will reside in. The board will run without it connected, using a regular ATX PSU, but if your graphics card can't get the power it needs from the slot or an external power source, you'll need to invest in a new PSU.
Underneath that connector, down the right-hand edge of the mainboard, are the PATA ports that hang off the nForce4 bridge's disk controller. The white one is the primary channel, the blue one the secondary. Auxiliary 12V power is next, the usual 4-pin connector sitting to the bottom left of the CPU socket area, a placement you'll be familiar with if you've run an Athlon 64 or Athlon FX system in the past.
NVIDIA then push the PEG16X slot far down the board, near the nForce4 silicon itself, by placing the PCI Express 1X expansion slots above it. There are two in total on the reference board. While the PEG16X slot is in roughly the same place on AIB partner boards based on nForce4, they'll juggle the PCI Express and PCI Conventional port counts to suit their expansion plans for a particular board. Expect to see various PCI Express peripheral port counts, ranging from just one to the full complement of four, as time goes by.
The PEG16X is close to the bridge for signal quality reasons. The shorter the path to the controller the better, in terms of signal strength and latency. Four PCI Conventional slots, in virginal white, sit underneath the PEG16X slot. The nForce4 bridge, naked in the press shot, is flanked on its right side by the four SATA ports the bridge natively supports. Partner boards also seem to be implementing Silicon Image's Sil3114 4-port controller initially, on the first batch of their nForce4 Ultra designs, giving you eight SATA ports (4 SATA300, 4 SATA150) to play with, along with IDE ports for legacy hard disks and optical devices.
The floppy port is last, lying on the bottom edge of the board, near the right side. It's a decent placement for it, if you can't squeeze it directly along that right hand edge where you see the PATA ports on the reference board.
In terms of board aesthetic, given that it'll host CPUs made in AMD's famous Fab 30 in Dresden, it's nothing like Pfund`s outrageous dairy in the city (something more akin to a DFI LanParty board), instead it's more like the functional and highly technical Volkswagen factory in the heart of old Altendresden.
nForce4 Ultra retail boards from board partners are very similar in layout, so getting to know the reference board will stand you in good stead for any purchase of nForce4 Ultra in the near future.
